I have been having the nightmare of nightmares! It started out with just doing a simple cam change or so I thought.I had a 214/214@50 443 lift cam not much of a cam. I got a Comp 268 xetreme cam to put in and I just can't figure out what is up. I have went through the entire engine (rings ,bearings,polished crank,valve job,cam,timing chain) the whole thing , now i'am putting it back togather and don't seem to have any piston to valve clearance. It is just a 480 lift cam iam using Sliv-lite Hypereutectic pistons with 4 valve reliefs and iam using the L-31 Vortec heads. My deck height is .050. I know that there is alot of guys are running this combo with no problem. Iam sure that iam doing something wrong with my timing, I set it up with the timing marks just as the book says (or so I think) and just at top dead center or just before the intake valve hits the piston. I was doing the clay deal to check the piston to valve clearance and its a good thing or I could have had one H--L of a mess. I don't know if I have given enought info for anyone to give me any feedback on but if so please get back with me. Thanks NORT

 

Yea, that cam shouldnt have a problem...

Is the dowel pin lined up with the hole in the cam sprocket? That or the cam was ground wayyyyyy off.

 

Recheck the timing chain. With #1 cylinder at TDC the timing marks on the gears should be lined up together. The crankshaft keyway should be around the 2 o'clock position.

Are you using standard 1.5 rockers or higher 1.6 ones?

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87 IROC-Z SuperPro ET Bracket Race Car
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all the flat tops pistons i've ever used or checked would need a cam with over .600 lift and i do mt checking without a gasket so you can add another .040 to that. i agree i'd go back and make sure the dowel and gears are correct and degree the cam to see if it's ground wrong.

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ICON Motorsports

1st & 3rd
MM Black Diamond 538 F&AM

 

if you cant get it figured out, call the comp cams tech line and see what they suggest for you

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Sounds to me like the cam is out of time...

Locate the #1 piston at TDC; the crank key is eaxctly lined up with it, so it should be pointing exactly at 45°, and at that point the mark on the crank gear should be straight up... take the cam gear off, take the chain off, put the gear back on with one bolt finger-tight and turn the cam so that the mark on the gear points straight down; take the bolt out, and put the gear back on.

You should not be having clearance problems. In fact, you should have at least .350" of clearance with it properly timed. It's even possible that the valves shouldn't hit the pistons at all no matter what the cam timing is, I know that at .410" of lift, the valves miss the pistons altogether with a broken timing chain (BTDT a couple of times in my life).

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ICON Motorsports

 

Another thing to check is to make sure that's the correct cam. Look at the grind number on the front of the cam. It should be 12-242-2